SYRPHIDAK OF MAINE. 253 



is broader, the third segment black except a quadrangular spot in front 

 on each side. Front and middle legs yellow, except on the basal half 

 or more of the femora, black ; hind legs black, the knees only yellow. 

 Description adapted from Williston (62, p. 207) and Verrall (55, 

 p. 57i). 



SYRITTA PIPIENS Linne. 



This is one of our most abundant and wide spread species, 

 apparently occurring throughout most of Europe and North 

 America and common from spring to autumn. It has been 

 recorded breeding in horse-dung and cow-dung in Europe (17), 

 and Dr. L. O. Howard has noted the capture (but not the rear- 

 ing) of an adult about human faeces. 



The larvae were found breeding in large numbers in moist 

 masses of guinea-pig manure in the animal room at Ohio State 

 University during the winter and spring of 1915. On July 7 

 at Orono, two puparia were taken from a drying mass of 

 human excrement at the opening of a sewer. Adults emerged 

 from them August 2 and 3. On July 7 and 12 a number of 

 females were found hovering about the above-mentioned mass 

 of filth. Two of them were enclosed in a vial and had soon 

 deposited a mass of several hundred eggs. They began hatch- 

 ing on July 1 6, the duration in the egg-stage having been 

 almost exactly four days. 



This species in all its stages shows a close resemblance to 

 Tropidia quadrata and it will be described in comparison with 

 that species. 



F-9Q- (Fig- 37-i, 2, 3}. Sub-cylindrical, tapering toward the ends; 

 the micropylar end somewhat truncate, the opposite end rounded out; 

 nearly straight on the ventral side, somewhat rounded up dorsally. 

 Dimensions (ten specimens) : Length .6325 to .6875 mm., average .665 

 mm. ; maximum diameter .213 to .24 mm., average .23 mm. 



The sculpturing of the chorion consists of polygonal elevated areas, 

 separated 1 by narrow depressed lines which form a darker network 

 over the entire surface. About thirty such elevations the length of 

 the egg, fifty to sixty around it. With higher magnification (1-4 in. 

 objective) these elevated areas are seen to be finely papillose, and on 

 closer examination the papillae are seen to be grouped into areoles of 

 greater elevation, with depressions between them. As contrasted with 

 T, quadrata, it is evident that the grouping of the papillae into definite 

 rounded areoles is much less pronounced and that the areoles are 

 much more irregular in shape (Fig. 37-,?; cf. fig. 36-7). For example 

 on the egg of T. quadrata the areoles are quite easily seen with a 2-3 in. 



